The present invention relates generally to a method and an apparatus for the group control of elevators with double cars and, in particular, to a method and an apparatus for determining the elevator optimally available for assignment for serving a floor call.
In a group control for elevators with single cars, disclosed in the European Pat. No. 0 032 213, assignments of the floor calls to the cars are optimized by the time to serve which is dependent on the distance from the call. In this patent, a sum of the time losses proportional to the waiting passengers and the time losses of the passengers in the car is calculated from the distance between the floor and the car position indicated by the floor selector, the intermediate stops to be expected within this distance and the instantaneous car load. The calculation is performed by means of computing equipment, such as a microprocessor, during a scanning cycle of a first scanner at every floor, whether a floor call is present or not. The car load existing at the instant of calculation is corrected in such a manner that the anticipated leaving passengers and entering passengers, derived from numbers of passengers leaving and entering in the past, are taken into consideration at the future intermediate stops. This sum of losses, also called operating costs, is stored in a cost memory. During a cost comparison cycle aided by a second scanner, the operating costs of all the elevator cars are compared with each other in a comparator circuit. For each comparison, an assignment command can be stored in an assignment register of the elevator car with the lowest operating costs, which assignment command designates that floor to which the respective car is assigned optimally in time.
The Swiss Pat. No. 660,585 discloses a control for an elevator group with double cars in which the group control described above has been improved in such a manner that the assignment of the individual cars of double car elevators to the floor calls can be optimized by time. The operating costs are calculated for each of the two individual cars of a double car elevator and are compared with each other by means of a comparator circuit, wherein the lower operating costs are stored in the cost memory of the respective elevator. In response to the presence of assignment commands for equidirectional floor calls of two neighboring floors and/or coincidences of car calls and floor scanner positions, the operating costs to be stored are reduced. This control for the elevator group interprets the double car as two individual cars which compete with each other.
The sum of losses or operating costs, disclosed in the European Pat. No. 0 032 213, is solely dependent on the position and the direction of the calls, on the car load and on the operational status of the car, and is calculated, as in the Swiss Pat. No. 660,585, for each individual car of the double car. In such a calculation, the mutual influences and relationships between the two individual cars are not fully taken into account. The lower operating costs of the individual cars of a double car are then stored in the cost memory of the corresponding elevator and compared for each floor with the lower operating costs of the other double cars in the elevator group. In controls of this type, the floor calls are not assigned to the optimal double car, but to the optimal single car. A uniform distribution of the passengers in the double cars in the elevator group is therefore impaired during normal operation of the elevator installation. By the separate calculation of the operating costs of the two individual cars, only coincidences of car calls of the respective car and floor scanner position can be promoted by a reduction of the operating costs of the respective car. The stopping at neighboring floors, where the other individual car not participating in a car call is concerned, is not promoted. An optimal assignment of the floor calls to the double cars is therefore not possible in all cases. From the above, it can be inferred that a group control for elevators with double cars, which considers the two cars of a double car as a single car, cannot achieve optimum results with respect to a minimum number of stops, short average waiting times of the passengers and an increased transport capacity.